A practical and scalable synthesis of a Fmoc‐protected tricyclic dipeptide mimetic (6), that is, a 1,4‐diaza‐tricyclo‐[8.3.03, 7]‐tridec‐8‐ene derivative resembling a rigidified di‐L‐proline in a polyproline type II (PPII) helixconformation, was developed. The strategy is based on a Ru‐catalyzed ring‐closing metathesis of a dipeptide (4) prepared by PyBOP coupling of cis‐5‐vinylproline tert‐butylester